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A women digs her vehicle out of the snow in Bayonne, New Jersey

A huge snow storm is blanketing the densely populated US North-east, after wreaking havoc with ice in the South.

Across the typically mild South, about 750,000 homes and businesses lack power, and about 6,500 flights have been cancelled.

The weather system has affected people in about 22 states from Texas to Maine and caused at least 18 deaths.

The storm dumped up to 15in (30cm) of snow in the Washington DC region and 8in around New York City overnight.

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The federal government shut down its offices on Thursday

Snow-covered streets were deserted during the morning commute in the nation's capital, where the federal government shut down its offices.

As much as 10-20 inches of snow in total could fall from north-eastern Pennsylvania to New England on Thursday, said the National Weather Service.

Almost 6,500 flights were cancelled on Thursday, according to airline-tracking website FlightAware.com.

While temperatures at the Winter Games in Sochi, Russia, rose to 17C (63F), the US was shivering in bitter cold once again.

In New York City, Mayor Bill de Blasio was criticised for keeping schools open despite the snow piling on the ground.

"Why [aren't] schools all around NYC closed? It's going to take some kid or kids getting hurt before this goofball policy gets changed," Al Roker, a prominent meteorologist and television figure on NBC, wrote on Twitter. He is currently in Sochi, Russia, for the Olympics, but has a child in a city school.

Mr de Blasio responded that many parents depended on schools to watch over their children while they work.

Winter celebration cancelled

Ironically, a celebration of winter tourism in the village of Lake Placid, New York state, was cancelled because of the storm.

Described by the National Weather Service as an event of "historical proportions", the storm leaves in its southern wake a wreckage of snapped tree branches and power lines coated in as much as an inch of ice, motorways turned to car parks, road accidents and residents shivering in darkened homes.

Forecasters said it was one of the worst storms to strike Atlanta, the largest city in the South, since 1973.

President Barack Obama declared a disaster in the state of South Carolina and all northern counties in Georgia, opening the way for federal aid.

On Wednesday evening, the Federal Emergency Management Agency said it was moving supplies, including generators, meals, water, blankets and cots to an emergency centre in Atlanta.

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Media captionTraffic in areas of North Carolina ground to a halt and many had to abandon their cars for the night

At least 18 deaths have been blamed on the storm, many of them in traffic accidents.

Three people were killed on Wednesday when an ambulance slid off a west Texas road, flipped over and caught fire.

Meanwhile, a firefighter died when an out-of-control vehicle knocked him off an icy motorway bridge in Dallas, Texas. And a pregnant woman in New York City was killed after being struck by a snow plough. Her baby was delivered in critical condition via caesarean section.

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White-out at the White House

A man in Georgia was killed after slipping and falling on a patch of ice.

On Wednesday, thousands of vehicles were stranded on snow-shrouded motorways around Raleigh, North Carolina, with some people abandoning their vehicles.

Soo Keith, of Raleigh, left her office shortly after midday, but after two hours had only driven a few miles.

She told the Associated Press news agency she eventually abandoned her vehicle and continued on foot, arriving home four hours later.

"My face is all frozen, my glasses are all frozen, my hair is all frozen," said Ms Keith.

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Umbrellas were no match for the storm in New York City

Residents of Georgia appeared to have heeded official warnings, with motorways in the state clear but with many people stuck at home without electric power.

"Thanks to the people of Georgia," Governor Nathan Deal said. "You have shown your character."

Mr Deal asked those waiting for power to be restored to be patient, saying he was hearing of "good response times" from the state's utilities.

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Stuck vehicles were slowly getting back on the road after traffic chaos in Raleigh, North Carolina

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The Empire State Building seen from a snowy path in the New York City borough of Queens

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A man on skis by the US Congress building, Washington DC